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Cerium dioxide (CeOe-x) deviates trongly from stoichiometry at elevated temperatures and reduced partial pressures of oxygen (po2) to produce an oxygen deficient n-type semiconductor. Measurements of electrical conduc-tivity and thermoelectric power as a function of Poe were performed on single crystals of CeO2-x over an extended composition range (10.5 ~ x ~ 2.5 • 10-1) in order to: (i) remove the ambiguity concerning the identity of the dominant ionic defects, (ii) obtain the formation energies of appropriate defect species, and (iii) establish the composition ranges at which defect interac-tions set in. A system developed for generating and monitoring poe almost continuously, enabled the acquisition of data in previously unobtained critical ranges of Poe. A defect model which includes singly and doubly ionized oxy-gen vacancies and quasi-free lectrons was established by the excellent agree-ment found at small x between experimental ly obtained conductivity data and theoretical curves based on the model. Doubly ionized vacancies were shown
Tuller et al. (Thu,) studied this question.